Date of Award
Master of Science in Zoology
Kerwin E. Hyland
The purpose of the investigation is to attempt to make female ticks of the genus Dermacentor radioactive with carbon-14 labeled glycine; to determine whether transovarial passage will take place; and to determine the effect of the isotope (C14) on the fecundity of the female and on the viability of the eggs.
A feeding method described by Chabaud and by Burgdorfer has been adapted for the administering of radioisotopes. Female ticks, Dermacentor variabilis and Dermacentor andersoni, were fed glycine. A micropipette calibrated to hold approximately 0.01 ml. of liquid was drawn out and fitted over the hypostome and chelicerae of the tick. The liquid was placed in the tube with a Pasteur pipette and the tick was allowed to imbibe. After the radioactive meal the females and unfed males were placed in plastic capsules on rabbits for the completion of engorgement. Engorged females were removed and placed in shell vials and allowed to lay their eggs. The number of eggs deposited and the per cent of hatching were determined for each tick. A determination of the level of radioactivity was made for each adult female immediately after her radioactive meal, and after she was removed from the rabbit. The count of radioactivity of eggs and larvae in lots of 200 each from each female was also taken.
Control individuals of Dermacentor andersoni deposited an average of 6959 eggs of which 5530 (79 per cent) hatched. Radioactive females of Dermacentor andersoni laid an average of 4696 eggs of which 3663 (66.7 per cent) hatched. Females of Dermacentor variabilis produced fewer eggs, but hatchability was greater. The control females laid 3108 eggs per tick and 2968 eggs hatched, representing a hatchability of 95.6 per cent. Radioactive ticks produced 2036 eggs, and of these 1916 hatched, resulting in a hatchability of 94.8 percent.
The amount of radioactivity of adult ticks was measured with the Geiger-Muller counter. Lots of ticks that had just finished their radioactive meal had average counts of 222, 1024, 665, and 1075 per minute. Engorged adults had an average of 286 counts per minute. Using the proportional flow counter, eggs and larvae in lots of 200 gave average counts per minute of 124 (for the eggs) and 57 (for the larvae). Attempts to measure radioactivity of eggs and of larvae with the Geiger-Muller counter were unsuccessful.
Statistical tests for significant differences between untreated and treated individuals revealed no effect of the specific concentrations of C14 glycine on either egg production or hatchability.
Hammar, Joanne L., "Administration and Transovarial Passage of Radioactive Glycine in the Genus Dermacentor (Acarina: Ixodidae)" (1959). Open Access Master's Theses. Paper 1494.